It is known that hydrogen can be obtained from aqueous solutions by visible light irradiation utilizing transition metal complexes or other chromophores as sensitizers. This system uses a sacrificial electron donor as the electron source. Water serves as the proton source. The following equations wherein Ru(bipy).sub.3.sup.+2 is the photosensitizer, methylviologen (MV.sup.+2) is the electron acceptor and ethylenediaminetetraacetic acid (EDTA) is the sacrificial electron donor illustrates this method: ##STR1## where MV.sup.+2 /MV.sup.+ represents a possible electron relay.
In this system MV.sup.+ acts upon water in the presence of metal catalysts to afford hydrogen; however, this system requires the addition of a sacrificial electron donor such as EDTA or triethanolamine (TEOA).
It is also known that oxygen can be generated from water by an analogous method in the presence of a sacrificial water by an analogous method in the presence of a sacrificial electron acceptor. According to this method visible light is absorbed by an aqueous solution of a sensitizer such as Ru(bipy).sub.3.sup.+3 in the presence of an electron acceptor such as cobalt ammine complexes. In this system Ru(bipy).sub.3.sup.+2 is oxidized to Ru(bipy).sub.3.sup.+3 and this respect, in the presence of a metal catalyst, oxidizes water to oxygen. Water itself serves as the electron source: ##STR2## where A represents a suitable sacrificial acceptor which upon reduction is irreversibly destroyed.
In this system Ru(bipy).sub.3.sup.+3 accepts an electron from water and thus regenerates the sensitizer cation Ru(bipy).sub.3.sup.+2 while at the same time generating oxygen.